Lewis Hamilton will start the Russian Grand Prix from tenth position on the grid after Mercedes avoided making any changes that would necessitate a potential penalty.
The defending champion suffered problems with his MGU-H during qualifying for Sochi race, identified as the same issue that hampered him during the Chinese Grand Prix too.
However, Mercedes have reverted to Hamilton's first engine from the opening round in Australia, whilst changing the turbocharger, MGU-H, electronics and energy store as allowed within the team's annual allocation.
A team spokesman explained that complications arose when ensuring the parts replaced were of the same specification due to an upgrade introduced this weekend.
As such, a new fuel system had to be flown out from the UK overnight and fitted to the spare Power Unit this morning. Mercedes also says the engine had been fired up successfully, meaning Hamilton is able to start on the fifth row.
Hamilton heads into the race looking to bridge the 36 point gap to Nico Rosberg in the standings, though the German starts from pole position.